Boris Bouchevreau

SMARTER crystallography of the fluorinated inorganic-organic compound Zn3Al2F12 center dot[HAmTAZ](6)

We present in this paper the structure resolution of a fluorinated inorganic-organic compound--Zn(3)Al(2)F(12)·[HAmTAZ](6)--by SMARTER crystallography, i.e. by combining powder X-ray diffraction crystallography, NMR crystallography and chemical modelling of crystal (structure optimization and NMR parameter calculations). Such an approach is of particular interest for this class of fluorinated inorganic-organic compound materials since all the atoms have NMR accessible isotopes ((1)H, (13)C, (15)N, (19)F, (27)Al, (67)Zn). In Zn(3)Al(2)F(12)·[HAmTAZ](6), (27)Al and high-field (19)F and (67)Zn NMR give access to the inorganic framework while (1)H, (13)C and (15)N NMR yield insights into the organic linkers. From these NMR experiments, parts of the integrant unit are determined and used as input data for the search of a structural model from the powder diffraction data. The optimization of the atomic positions and the calculations of NMR parameters ((27)Al and (67)Zn quadrupolar parameters and (19)F, (1)H, (13)C and (15)N isotropic chemical shifts) are then performed using a density functional theory (DFT) based code. The good agreement between experimental and DFT-calculated NMR parameters validates the proposed optimized structure. The example of Zn(3)Al(2)F(12)·[HAmTAZ](6) shows that structural models can be obtained in fluorinated hybrids by SMARTER crystallography on a polycrystalline powder with an accuracy similar to those obtained from single-crystal X-ray diffraction data.

An NMR‐Driven Crystallography Strategy to Overcome the Computability Limit of Powder Structure Determination: A Layered Aluminophosphate Case

Along with the growing complexity of many inorganic systems, structure determination from powders is getting more and more difficult, and represents a severe obstacle for the discovery of new materials. The lack of single crystals (or crystals of insufficient size or quality) unfortunately often rules out any structural determination. It is acknowledged that it is more difficult to get good-quality single crystals as soon as the cell volume of a structure increases. The challenge of structure elucidation of powders is very well reflected by the small number of new structures published per year that are determined from powder diffraction compared to the number of structures determined from single-crystal diffraction data. Aluminophosphates are no exceptions, with as little as eight structures in total determined from powder diffraction, out of the more than 250 structures reported in the database. For inorganic or hybrid powders, one of the key, but challenging, steps that prevents structure elucidation is the construction of an initial structural model. Strategies for enhancing the efficiency of powder-based structure determination have shown a continuous development, especially by incorporating direct space structural information. To assist this part, diffraction software products based on simulated annealing or Monte–Carlo global optimization in directspace like FOX, ESPOIR, TOPAS, and so on, have proven reliable strategies for structure determination of a wide range of solids. Alternative routes have been proposed for a drastic acceleration of the structure solution when prior knowledge of the constitutive building blocks is available, allowing to find the solution of extremely large cells. However, considering the frequent absence of such prior knowledge, these methods become unsuccessful due to the exponential explosion of computing time with the number of degrees of freedom in the unit cell. This constitutes a limit of computability causing a bottleneck for structure determination from powders. It is therefore necessary to overcome this limit to yield 100 % success by reducing the computational workload. Beyond the performance of computing facilities itself, a successful and rapid search is largely determined by the number of degrees of freedom involved in the crystal structure versus the amount of input (chemical, topological, geometric, and so on) injected in the search. Nuclear magnetic resonance spectroscopy associating state-of-the-art high magnetic fields, ultra-fast magic angle spinning (MAS), and tailored NMR pulse sequences has become an extremely powerful tool to provide information at the atomic level about the local environment of a given nucleus. In this contribution, we shall show with the example of a novel nano-perforated lamellar aluminophosphate, [Al5(OH) ACHTUNGTRENNUNG(PO4)3ACHTUNGTRENNUNG(PO3OH)4] [NH3ACHTUNGTRENNUNG(CH2)2NH3]2 [2H2O], hereafter referred to as AlPO4-(Al5P7)-DAE (DAE= diaminoethane), 1) how topological information extracted from NMR data, that is, an NMR-driven structure resolution, can be directly introduced in the structure-elucidation process, allowing the determination of an initial model, which was otherwise not possible despite the high quality of the synchrotron powder diffraction (SPD) data, 2) how the computation time necessary to search and converge to this model can be further drastically decreased by increasing the amount of NMR-based information up to the whole complex building blocks. This new methodology differs signifi[a] B. Bouchevreau, Dr. C. Martineau, Dr. F. Taulelle Institut Lavoisier de Versailles, UMR CNRS 8180 Universit de Versailles Saint Quentin en Yvelines 45 Avenue des Etats-Unis 78035 Versailles cedex (France) Fax: (+33) 139254277 E-mail : charlotte.martineau@chimie.uvsq.fr taulelle@chimie.uvsq.fr [b] Dr. C. Mellot-Draznieks Coll ge de France, 11 place Marcellin Berthelot Laboratoire de Chimie des Processus Biologiques FRE 34 88 CNRS, 75005, Paris (France) [c] Dr. A. Tuel IRCELYON, CNRS UMR 5256 Universit Lyon 1, 69626 Villeurbanne (France) [d] Dr. M. R. Suchomel Argonne National Laboratory Advanced Photon Source, Argonne, IL 60439 (USA) [e] Dr. J. Tr bosc, Prof. O. Lafon, Prof. J.-P. Amoureux Univ. de Lille Nord de France, UCCS USTL CNRS UMR 8181, 59652 Villeneuve d Ascq (France) Supporting information for this article is available on the WWW under http://dx.doi.org/10.1002/chem.201203767.

NMR crystallography driven structure determination: nanoporous materials

A summary of the recent results obtained in the field of NMR crystallography of nanoporous materials is proposed, and new original methods and strategies to perform NMR crystallography driven structure determination are presented. Although the work to reach structure resolution of a powder is much more difficult than for a single crystal, the use of NMR data associated with diffraction methods and modelling has provided significant successes in this domain. However, a general method to combine the different measurements, and overcome their respective limitations, has been only recently proposed. The structure search can therefore be organized to converge to possible structure models. This is of utmost importance for the structure determination of complex nanoporous crystals.

Structural study of calcium phosphonates: a combined synchrotron powder diffraction, solid-state NMR and first-principle calculations approach

The structures of four Ca-phosphonate phases are reported here: Ca(C6H5–PO3H)2 (1), Ca(C6H5–PO3)·2H2O (2), Ca(C4H9–PO3H)2 (3) and Ca(C4H9–PO3)·H2O (4). Structural models were obtained ab initio by using a combined synchrotron powder diffraction, solid-state nuclear magnetic resonance, and gauge including projector augmented wave (GIPAW) calculation approach. The 1H, 13C, 31P and 43Ca NMR parameters calculated from these structural models were found to be in good agreement with the experimental values, thereby indicating the high accuracy of the DFT-optimized structures. Correlations between the NMR parameters and structural features around the phosphonate were then analyzed, showing in particular the high sensitivity of the 31P asymmetry parameter ηCS and the 43Ca isotropic chemical shift to changes in local structure around the phosphonate groups and the Ca2+, respectively. Finally, the NMR data of a new mixed Na–Ca phosphonate phase, Ca1.5Na(C4H9–PO3)2, are reported.